Improving Data Throughput of CubeSats Through Variable Power Modulation

Nanosatellites, in particular, CubeSats, suffer from limited power and communication capabilities, which creates data throughput (DT) limitations imposing challenges on developers in implementing high data generating payloads, such as the ones deployed in Earth observatory missions. The study presents a framework-variable power modulation (VPM)-that involves varying the transmitter' s output power within the adjustable range, such that in the case of power availability, the transmission output power is increased accordingly. VPM allows optimal derivation of power for the transceiver, leading in an increase in the average pass duration, thereby providing higher DT. The implementation of VPM involves initiating communication with ground stations at lower elevation angles. However, this approach necessitates a thorough examination of the impact of small-scale fading, particularly Rician Fading, which can affect the signal reliability. In addition to VPM, the study also explores the integration of variable coding and modulation (VCM), a standard practice in communication systems. This article provides a comprehensive analysis of how VPM and VCM can collaborate to enhance the DT of CubeSats. Results from the study indicate that VPM can increase the DT of a standard 1U CubeSat by approximately 43%, while VCM alone can boost it by around 250%. When both VPM and VCM are combined, the DT experiences a remarkable improvement of approximately 340%. However, it is worth noting that the introduction of Rician Fading has a modest adverse effect, leading to a reduction in DT of up to 19%. It is important to highlight that while VPM does not necessitate complex or customized components for CubeSat adoption, it does require transceivers with in-flight configurability. Additionally, it is crucial to consider potential tradeoffs in link reliability when applying the proposed framework, as it can impact this aspect in certain scenarios.